155
FXUS02 KWBC 161901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
301 PM EDT WED JUL 16 2008
VALID 12Z SAT JUL 19 2008 - 12Z WED JUL 23 2008
PRELIMINARY UPDATE...
THE DETERMINISTIC GFS IS AGAIN AN OUTLIER AMONG THE BULK OF THE
00Z GUIDANCE WITH AT LEAST TWO CRITICAL SYNOPTIC SCALE
SYSTEMS...AND AS SUCH WAS NOT FACTORED INTO THE UPDATED MANUAL
FRONTS AND PRESSURES FOR DAYS 3 THROUGH 7. THE FIRST SYSTEM IS
THE TROUGH OVER THE EASTERN PACIFIC...WHICH IS CENTERED FARTHER
EAST ON THE 00Z GEFS MEAN...ECMWF...AND ECMWF ENSEMBLE MEAN...AS
WELL AS THE GEM GLOBAL AND UKMET. THE SECOND SYSTEM IS THE SHORT
WAVE TROUGH THAT SLIDES THROUGH THE GREAT LAKES...WHICH IS WEAKER
AND MORE PROGRESSIVE ON THE OTHER RECENT MODELS. THE CONSENSUS OF
THE OTHER GUIDANCE WITH THE PACIFIC SYSTEM IS TO SHEAR IT
NORTHEASTWARD MID PERIOD THROUGH THE PACIFIC NORTHWEST...AS
OPPOSED TO BRINGING IT BODILY INTO THE OREGON COAST WITH VIGOR
DAYS 6 AND 7 AS PER THE GFS. WITH THE SYSTEM CROSSING THE GREAT
LAKES...A TENDENCY TOWARD BLOCKING OVER EASTERN CANADA INDICATED
BY THE MAJORITY OF THE 00Z MODELS WOULD SEND THE IMPULSE ON A MORE
SUPPRESSED COURSE...WITH MUCH LESS RIDGING AHEAD OF IT OVER THE
NORTHEAST THAN THE MORE DEVELOPED GFS.
ALL THE MODELS SHOW A MORE OR LESS CLIMATOLOGICAL AXIS OF
MONSOONAL MOISTURE OVER THE SOUTHWEST...WITH THE RING OF FIRE
AROUND THE SUBTROPICAL RIDGE WRAPPING INTO THE SOUTHEASTERN
STATES. THE BLEND OF THE ECMWF AND ITS ENSEMBLE MEAN USED FOR THE
FRONTS AND PRESSURES MAY NOT WORK AS WELL FOR TEMPERATURES OVER
THE SOUTHWEST...WITH UNDULY SUPPRESSED VALUES THERE LIKELY RELATED
TO OVERSTATED COVERAGE OF CLOUDS AND RAINFALL WITH THE MONSOON IN
THOSE SCHEMES.
FINAL...
UNFORTUNATELY...THE 12Z DETERMINISTIC GFS IS STILL OUT OF SYNC
WITH ITS PEERS FROM THE NEW MODEL CYCLE...AND PERHAPS MOST
SIGNIFICANTLY...THE LATEST GEFS MEAN. IT STILL INSISTS ON
SWINGING A RATHER POTENT TROUGH INTO NORTHERN CALIFORNIA...AND
DOES NOT PHASE THE GREAT LAKES SYSTEM WITH THE BLOCK OVER
SOUTHEASTERN CANADA...WHICH LEADS TO A FUNDAMENTALLY DIFFERENT
REGIME OVER THE NORTHEAST AND MID ATLANTIC STATES. STUCK WITH THE
BLEND USED ON THE UPDATE PACKAGE FOR THE FINAL FRONTS AND
PRESSURES...WHICH WAS LARGELY SUPPORTED BY THE 12Z GEFS
MEAN...GEM...UKMET...AND DETERMINISTIC ECMWF.
CISCO
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